The present invention relates to die cutting machines for making carton blanks, and more particularly to a frame assembly for a lower blanking tool that supports carton scrap during a blanking operation in a die cutting machine.
In the manufacture of cartons, small sheets of paper material having specific profiles are cut out of larger sheets of paper material. These smaller sheets are known as carton blanks which, in turn, are formed into cartons and/or boxes. The blanks are formed during a process known as a blanking operation in a die cutting machine.
In a die cutting machine, the blanks are cut, but not removed from a large sheet of paper material. After the blanks have been cut, the sheet is moved downstream in the die cutting machine to a blanking station where the sheet is positioned over a frame assembly for support. The frame assembly includes an outer frame and an inner grid having large openings which correspond in size, in shape and in position to the profile of the carton blank previously cut. Below the frame is a mechanism for stacking the carton blanks.
At the blanking station, an upper tool is used in combination with the lower tool or frame assembly to knock the carton blanks from the sheet of paper material while holding the scrap material that surrounds the blanks. The upper tool has a support board that moves vertically up and down in the die cutting machine, and the support board typically has a plurality of stand-offs depending therefrom that hold pushers spaced beneath the board which in turn are used to push the carton blanks from the sheet through the lower tool or frame assembly. A plurality of presser assemblies are also mounted in the support board and depend therefrom to hold the scrap material against the lower tool or frame assembly during the blanking operation so that the blanks may be pushed from the sheet. A presser assembly typically includes a presser rail which is biased downwardly away from the support board by a spring so that the rail is positioned slightly below the pushers. As the upper tool is lowered, the presser rail engages the sheet of paper material first such that a scrap portion of the large sheet of material is secured between the presser rail and the frame. The upper tool then continues to be lowered such that the sheet of material engages the inner grid within the frame while at substantially the same time the pushers engage the carton blanks and knock the blanks out of the sheet of material and through the inner grid. The carton blanks then fall into a stacking mechanism below the frame where the blanks are stacked for further processing.
The lower tool used in the blanking operation is typically comprised of a steel outer frame that supports an inner grid. Steel was used because of its inherent strength and stiffness, but steel also significantly increases the weight and cost of the lower tool. In the past, it was thought that materials such as aluminum, although lighter and easier to process than steel, could not be used for the lower blanking tool because aluminum would not have sufficient strength or stiffness and would be too flexible to withstand the constant abuse taking place during a blanking operation.
The frame and grid support a sheet of paper material during the blanking operation, and thus the grid must be configured to match or conform to the die cut in the sheet of paper material. In addition, the grid must be reconfigured whenever a different carton blank needs to be produced. Unfortunately, due to manufacturing tolerances and the like, outer frames are not always xe2x80x9csquarexe2x80x9d and rigid. In addition, the grid may not always be positioned with high precision within the outer frame since the attachment pieces which hold the grid onto the frame can move slightly during assembly and thus alter the desired position of the grid.
It is an object of the present invention to provide an improved frame assembly for a lower blanking tool of a carton die cutting machine.
It is another object of the present invention to provide a frame assembly for a lower blanking tool that is composed of aluminum, but yet which is durable and rigid during a blanking operation.
Yet another object of the invention is to provide a frame assembly for a lower blanking tool which is easy to assemble, compatible with standard blanking operation machinery, and relatively inexpensive.
In order to accomplish the above objects, the present invention provides a frame assembly for a lower blanking tool of a carton die cutting machine. The frame assembly includes an outer frame for supporting a sheet of die cut paper material during a blanking operation wherein the sheet of paper material defines a substantially horizontal plane. The outer frame includes a pair of opposite, spaced apart longitudinally extending side rails, and a pair of opposite, spaced apart cross rails extending crosswise between the side rails. The side rails and cross rails are all preferably composed of extruded aluminum. Each of the cross rails have an inner surface disposed substantially transverse to the plane defined by the sheet of paper material and have a T-shaped slot formed therein opening to the inner surface. Each of the side rails have an upper surface disposed substantially parallel to the plane defined by the sheet of paper material and have a T-shaped slot formed therein opening to the upper surface. Each of the T-shaped slots define a downwardly extending axis disposed at an acute angle with respect to the plane defined by the sheet of paper material. Finally, the frame assembly includes a plurality of corner pieces which rigidly interconnect the rails together. Each of the corner pieces includes fasteners extending into the T-shaped slots of adjacent side and cross rails. The downward extending axis of each T-shaped slot together with the design of the corner pieces compensates for any geometric or extrusion tolerances in the side and cross rails so that high precision may be maintained to insure that the frame remains square.
In other aspect, the invention includes a frame member for a lower blanking tool frame assembly of a die cutting machine. The frame member comprises an elongate rail having an upper surface, a lower surface, an outer surface and an inner surface. The rail has a bolt receiving T-shaped slot formed therein which opens to the inner surface of the elongate rail and defines a downwardly extending axis disposed at an acute angle with respect to the inner surface of the rail.
In yet another aspect, the invention includes a corner piece for interconnecting the frame members or rails of the lower blanking tool frame assembly used in a carton die cutting machine. Each corner piece includes an L-shaped body having a horizontal plate member defining a substantially flat upper face, a substantially flat opposite lower face, an inside face, an opposite outside face, and an end face. The L-shaped body also includes an upright plate member defining a substantially flat inner face contiguous with the upper face of the horizontal plate member, a substantially flat outer face contiguous with the lower face of the horizontal plate member, an inside face contiguous with the inside face of the horizontal plate member, an opposite outside face contiguous with the outside face of the horizontal plate member and a top face. The horizontal plate member has at least one outwardly extending bolt receiving bore formed therethrough which defines an axis disposed at an acute angle with respect to the upper and lower faces of the horizontal plate member. The upright plate member has at least one downwardly extending bolt receiving bore extending therethrough which defines an axis disposed at an acute angle with respect to the inner and outer faces of the upright plate member. The corner piece also includes a lip projecting outwardly from the outer face of the upright plate member and a tenon projecting downwardly from the lower face of the horizontal plate member. The primary advantage of the corner piece of the present invention is that as fasteners extending therethrough into the T-shaped slots of the rails of the frame assembly are tightened, the corner pieces properly locate the side rails and cross rails and at the same time pull the side rails and cross rails into a xe2x80x9csquarexe2x80x9d or 90xc2x0 relationship. The corner pieces also rigidly interconnect the side and cross rails together so that a frame assembly of high precision can be utilized in the blanking operation of a carton die cutting machine.